Oscillation drive mechanism



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United States Patent 3,442,145 OSCILLATION DRIVE MECHANISM HerbertLemper, Pittsburgh, Pa., assignor to Mesta Machine Company, Pittsburgh,Pa., a corporation of Pennsylvania Filed Aug. 8, 1967, Ser. No. 659,210Int. Cl. B22d 27/08; F16h 25/08, 54/04 U.S. C]. 74-54 8 Claims ABSTRACTOF THE DISCLDSURE An oscillation drive mechanism is disclosedparticularly for use in oscillating the mold structure of a continuouscasting machine and for analogous applications. The mechanism includesan output cam member having a plurality of generally parallel cammingsurfaces thereon. The cam member is keyed for rotation with an elongatedoutput shaft but is slidably movable therealong to juxtapose a selectedone of the camming surfaces to a cam follower. The camming surfaces canbe individually shaped to produce a substantially similar movement ofthe cam follower in one direction at a given rotational speed of the cammember but to produce correspondingly differing rates of cam followermovement in the opposite direction at such given rotation speed. Theoscillation drive mechanism is particularly useful in connection with acontinuous casting machine wherein the mold structure may be driven atdifferent rates in the forward direction depending upon the castingspeed but desirably is returned as quickly as possible in the oppositedirection irrespective of casting speed for maximum production.

The present invention relates to an oscillation drive mechanism and moreparticularly to such mechanism arranged for producing optimum moldoscillation in continuous casting machines for analogous application.Specifically, the invention relates to novel means of the characterdescribed for moving a mold somewhat faster than the casting speed inthe casting direction but is returned in the opposite direction atseveral times this speed and preferably as rapidly as practicalirrespective of the forward or downward speed.

My invention is exemplarly useful with continuous casting machines suchas are disclosed in the copending and coassigned application of HerbertLemper et al. filed Mar. 6, 1967, Ser. No. 620,779". Such continuouscasting machines are commonly utilized throughout the steel industry forthe continuous production of slab or billet strands. A continuouscasting machine may be capable of producing one or more of such strandsdepending upon the particular machine in question. Each of the strandsusually originates at an oscillated mold structure provided with acooling jacket.

The molten steel or other metal poured into the continuous casting moldforms a solidified outer shell adjacent the walls of the mold.Successive shell portions are stripped off by the oscillating moldstructure and as the strand travels away from the mold the molteninternal portion thereof progressively solidify.

In order to eliminate thickening of the casting to the mold and to avoidthe application of tensil stresses to the newly formed casting, thecasting desirably is subjected to negative stripping, i.e., the moldstructure is moved somewhat faster forwardly or in the direction of themoving strand to strip that casting portion within the mold structure.When the mold structure is returned in the opposite direction it isdesirable to move the mold structure as fast as possible in order toachieve maximum production. The return cycle of the mold oscillation, of

course, separates the stripped casting portion from the mold so that themold structure can be refilled.

In conventional continuous casting machines, the mold structure isoscillated by means of suitable drive mechanism including a cam. The cammust be provided with a configuration to render an optimum oscillationcurve at the highest anticipated casting speed. At such speeds the moldstructure is desirably returned at a speed which is two to three timesfaster than the forward motion or negative strip of the mold structure.Unfortunately, when the continuous casting machine is slowed down asdemanded by particular casting operations or conditions, the returnstroke of the mold structure is correspondingly but unduly slowed,although the speed of the forward stroke is satisfactory. The timewasted during the correspondingly slower reverse strokes would providetime for a greater number of forward strokes. Hence, if it were possibleto reduce the forward speed of the mold structure without at the sametime reducing the return speed thereof the overall casting speed andattendant production of the continuous casting machine could beincreased, in comparison to conventional practices, when slower forwardrates are resorted to. Putting the matter somewhat differently, it ishighly desirable to return the mold structure to its starting positionas fast as possible during each oscillation irrespective of its forwardspeed. A realization of this desirable result would obtain an optimummold oscillation characteristic and attendantly a maximum productionrate.

This desirable result has previously been attempted -with hydraulicdrives. These attempts have not been eminently successful owing to thehigh maintenance costs of the hydraulic drives, particularly in the hightemperature environment to which they are subjected. Further, hydraulicdrives introduce intolerable inaccuracies into the oscillationcharacteristic of the mold structure as a result of load changes and theinevitable leakage and changes in fluid viscosity of the hydraulicfluid.

I overcome these disadvantages by providing an electromechanica-larrangement for approximating the aforementioned optimum oscillationcharacteristic Without encountering any of the aforementioneddisadvantages associated with hydraulic drives. More specifically, Iprovide a drive mechanism for mold oscillation involving a plurality ofcamming surfaces which are appropriately contoured to produce thedesired forward speed of the mold structure and to return the moldstructure as rapidly as possible irrespective of the selected forwardrate. I also provide novel means for supporting and shifting the cammingsurfaces as part of my disclosed oscillation drive mechanism. The drivemechanism can include the selflocking worm gear and helical or spur geartrain, disclosed in the aforementioned copending application, forcoupling the camming surfaces to suitable drive means.

I accomplish these desirable results by providing an oscillation drivemechanism including output camming means, a cam follower engageable withsaid camming means, means for rotatably mounting said camming means,means for rotating said cam means, said camming means having a pluralityof camming surfaces positioned thereon, and means for selectivelyjuxtaposing said camming surfaces to said cam follower.

I also desirably provide an oscillation drive mechanism wherein saidcamming means are mounted upon an elongated output shaft for rotationtherewith, slidably engageable keying means are positioned on said shaftand on said camming means, and said camming means slidably engage saidshaft and for movement therealong.

I also desirably provide an oscillation. drive mechanism wherein pivotedpositioning means are mounted for movement generally parallel to saidoutput shaft, said positioning means having an extension engaging ajournal therefor on said camming means for slidably moving said cammingmeans with pivoting movements of positioning means.

I also desirably provide an oscillation drive mechanism wherein saidcamming surfaces are provided with similar camming portions so thatmovements of said cam follower in one direction thereof are atsubstantially the same rate for a given speed of said mechanismirrespective of the preselected one of said camming surfaces, but saidcamming surfaces are provided with respectively differing cammingsurfaces for moving said cam follower in a generally opposite directionof movement at correspondingly differing rates at said given speed.

During the foregoing discussion, various objects, features andadvantages of the invention have been set forth. These and otherobjects, features and advantages of the invention together withstructural details thereof will be elaborated upon during theforthcoming description of certain presently preferred embodiments ofthe invention and presently preferred methods of practicing the same.

In the accompanying drawings I have shown certain presently preferredembodiments of the invention and have illustrated certain presentlypreferred methods of practicing the same, wherein:

FIGURE 1 is a front elevational view of one form of mold oscillationdrive mechanism arranged in accordance with my invention;

FIGURE 2 is a vertically sectioned view of the apparatus shown in FIGURE1 and taken along reference line IIII thereof;

FIGURE 3 is a partial right side elevational view of the apparatus asshown in FIGURE 1;

FIGURE 4 is an enlarged, partial, sectional view of the apparatus asshown in FIGURE 3 and taken along reference line IV-IV thereof;

FIGURE 5 is a partial cross sectional view of the apparatus as shown inFIGURE 2 and showing one of the cam lobes thereof;

FIGURE 6 is a similar view of another of the cam lobes;

FIGURE 7 is a similar view showing another of the cam lobes;

FIGURE 8 is a graph showing the development of the camming surfaces ofthe aforementioned cam lobes; and

FIGURE 9 is a graph illustrating comparative rates of oscillatorymovement of the mold structure corresponding to use of theaforementioned cam lobes;

FIGURE 10 is a graph illustrating optimum useage of the aforementionedcam lobes for a given application.

Referring now more particularly to the drawings and initially to FIGURES1 and 2 thereof, an exemplary form of my novel oscillation drivemechanism 10 is shown therein. The drive mechanism 10 includes anelectric motor 12 provided with tachometer 14 and coupled to worm shaft16 through a conventional flexible coupling 18. The shaft 16 isrotatably mounted on bearings 20, 22, and Worm 24 mounted on the shaft16 for rotation therewith engages worm gear 26 as better shown in FIGURE2. Worm gear shaft 28 is coupled to cam shaft 30 through enmeshed leftand right hand helical gears 32 and 34. Understandably, of course, spurgears (not shown) can be substituted for the helical gears 32, 34. Theworm gear shaft 28 is rotatably mounted on bearing assemblies 36 and 38which in turn are mounted on power train case 40. The cam shaft 30 issimilarly mounted.

A multilobed camming member 42 is slidably mounted on the cam shaft 30but is keyed for rotation therewith by a pair of splines 44 and 46seated in grooves 48 extending longitudinally in the outer surface ofthe cam shaft 30 as better shown in FIGURE 2. The cam member 42 includesa complementary central opening and thus is free to slide along thelength of the cam shaft 30 between its helical gear 34 on the one hand,and cam shaft bearing 38 on the other. Such lateral movement of the cammember 42 is controlled, however, by means described below. In thisexample, the cam member 42 is provided with three lobes or cammingsurfaces 50, 52 and 54, the individual contours of which are bettershown in FIGURE 1 of the drawings. Although three of said camming lobesare illustrated, it will be readily understood that a different numbercan be employed depending upon the application of the invention.

A pivotally mounted cam follower 56 having follower wheel 58 rotatablymounted thereon is positioned for engagement with a selected one of thecam member lobes 50, 52 or 54. The cam follower 56 is secured to camfollower shaft 58 which in turn is rotatably mounted on front and rearextensions 60, 62 of the upper portions of the casing 40. The followerwheel 58 is rotatably mounted on depending arm 64 of the cam follower56.

A cam follower 56 thus is oscillated vertically (as viewed in FIGURE 1)by the engagement between one of the cam member lobes and follower wheel58 which extends through access aperture 66 in the top of the casing 40.Desirably, the casing opening 66 is sealed by bellows 68 extending fromthe casing 40 to the cam follower 66 as better shown in FIGURE 1.

The oscillating movements of the cam follower 56 are translated intosimilar but opposed movements of mold structure 70 through pivoted beam72 and associated link members 74 and 76.

The cam member 42 is shifted along the length of the cam shaft 30 tobring a selected one of the lobes 50-54 into engagement with followerwheel 56. As shown in FIGURE 2 of the drawings, the cam member 42 ismoved to a position adjacent its right hand limit of travel such thatthe lobe 50 is engaged by the follower wheel 56. In accordance withanother feature of my invention, I provide positioning means for quicklyand positively positioning the cam member 42 to bring preselected onesof the lobes 50-54 into such engagement.

With reference now more particularly to FIGURES 1-3 of the drawings, oneform of such position means includes a rotatably mounted shaft 78 havingone end thereof protruding from the casing 40. A shifting arm 80 and anactuating arm 82 are affixed to the shaft 78 for rotation therewith. Theshifting arm 80 is positioned within the casing -40 as better shown inFIGURE 1 and is provided with rotatably mounted cam follower wheel 84positioned to ride in journal 86 of the cam member 42 (FIGURE 2). Infurtherance of this purpose the shifting arm journal wheel 8-4 isrotatably mounted on headed stub shaft 88, which in turn is rotatablymounted on lateral extension 90 of the shifting arm 80, as better shownin FIGURE 4. By this arrangement, angular displacement of the shaft 78induces similar movement of the arm 80 and journal wheel 84 between thesolid outline position of the camming member 42 in FIGURE 2 and itschain outline position 92.

The shaft 78 and shifting arm 80 can be selectively moved between thesetwo limiting positions by movement of actuating arm 82, which isprovided with operating handle 94 for this purpose as better shown inFIGURES 1 and 3. In this arrangement, actuating arm 82 is positioned byan index plate 96 having indexing apertures 98, 100, 102 as better shownin FIGURE 3. Thus, actuating arm 82 can be juxtaposed to a selected oneof the index apertures 98-102 to produce corresponding movements of theshifting arms 80 as noted by its solid outline position in FIGURE 2 andchain outline positions 104, 106 of its journal wheel 84 respectively toselectively position cam member 42 at its solid outline position (FIGURE2), its chain outline position 108 and its chain outline position 92.These movements selectively bring cam lobes 50, 52 and 5 4 respectivelyinto engagement with the follower wheel 58.

The handle 94 is of conventional construction and includes a springloaded plunger 110 (FIGURE 3) capable of partial entry into a selectedone of indexing apertures 98, 100, 102 to retain the handle '94 andactuating arm 82 thereat.

Referring to FIGURES 1, 2, 5-9 of the drawings, exemplary cammingconfiguration of the cam lobes 50-54 are illustrated. As better shown inFIGURE 1, it is assumed that cam member 42 is rotated in the directionof arrow 134 to produce oscillatory movements of the mold structure 70as noted by arrows 136 and 138. Thus, each of the cam lobes 50-54 isprovided with configurations 140, 141, 142 (FIGURES 5-7) respectivelywhose first differentials are substantially linear (FIGURE '8) and whichproduce corresponding upward movements of cam follower 56 and downwardmovements of the mold structure 70 at substantially constant velocities143, 144, 145 respectively (FIGURE *9) as denoted by arrow 136.Accordingly, the mold structure 70 is moved downwardly twice (FIGURES5-9) during each revolution of the cam member 42. With this arrangementthen the downward or forward cycles of the mold structure oscillationswill be at substantially constant but differing and progressively slowervelocities for a given speed of the oscillation drive mechanismdepending upon that one of the lobes 50-54 which is engaged with the camfollower 56, owing to the first differential line of the rise cammingportions 140-142 of all of the cam member lobes 50-54; Constantvelocities in the forward direction of the mold structure are highlydesirable for efiicient negative stripping.

On the other hand, the dwell configurations 146, 147, 148 (FIGURES 5-7)of cam lobes 50, 52, 54 respectively are of progressively lesser angularsegments (cf. FIGURE 8) of their related cam lobes 50-54. (In thisconnotation the term rise and dwell refer to the correspondingdirectional movements of cam follower 56.) The dwell configurations146-148 permit the cam follower 56 when selectively engaged with thecamming lobes 50-54 to descend with suitable acceleration anddeceleration as indicated by the cam development curves 146, 147, 148 ofFIGURE 8 and by corresponding rate curves 149, 150, 151 of FIGURE 9,which as noted previously are the first differentials of the camdevelopment curves of FIGURE 8. Thus the acceleration-decelerationcurves 149, 150, 151 of FIGURE 9 denote average rates in this example oftwo, three, and five times that of the corresponding ascending ratecurves 143, 144, 145. The mold structure 70, during its return stroke ismoved first at an accelerating rate 149a, 15011, or 151a (FIGURE 9)followed by a decelerating rate 1491;, 150b, 1511;. These accelerationand deceleration rates are adjusted as denoted by the dwell developmentcurves 146, 147, 148 of FIGURE 8 such that the integrated areas underthe return rate curves 149-151 of FIGURE 9 are equal to /2, A and /5 theintegrated areas under forward velocity curves 143-145 respectively.This establishes the necessary average rates of the mold structure 70during its return strokes to re turn the mold structure within timeintervals equal to /z, /3 and /5 of the forward stroke time intervalswhen the cam follower 56 is selectively engaged with cam lobes 50, 52,54 respectively.

From the exemplary configurations of the several cam lobes 50-54 asshown, it will be seen that the cam lobe 50 in this example is providedwith a rise time to dwell time ratio of 2:1 producing a correspondingaverage reverse speed of the mold structure equal to twice its forwardvelocity. Cam lobe 52 affords a similar speed ratio of 3:1 and cam lobe54, 5:1. These typical ratios can readily be varied to meet productionranges in specific applications of my invention. Thus, one or more ofthe aforementioned speed ratios can be changed by varying the rise anddwell configurations of one or more of the cam lobes 50-54 in accordwith the principles of the invention inherent in FIGURES 8 and 9.

With the arrangement shown, the mold structure 70 can be returned at amaximum speed during its reverse stroke although its forward stroke isslowed considerably by decreasing the speed. of the oscillation drivemechanism 10 in accordance with production conditions. Ac-

cordingly, loss of production is not entailed by slow return strokes ofthe mold structure 70 although certain casting conditions requireslowing down the forward strokes of the mold structure 70.

A typical useage of my oscillation drive mechanism 10 is illustrated inFIGURE 10 of the drawings, wherein oscillations per minute of the moldstructure is plotted against casting speed in inches per minute. Thevariously shaded areas 152, 154, 156 correspond respectively to useageof cam lobes 50, 52, 54 of the oscillation drive mechanism 10. Empericalcurves 158, 160 denote the optimum times for shifting the cam member 42,in this application, from the cam lobe 50 to the cam lobe 52 and fromthe cam lobe 52 to the cam lobe 54 respectively depending uponproduction conditions. The families of curves shown in each shaded area152, 154, or 156 correspond to indicated oscillational amplitudes, inthis example of /2 inch to 1 /2 inches respectively, or inch to 1 /2inches for the shaded area 152, resulting from use of a selected one ofcam follower apertures 158, 160, 162, 164, 166 respectively (FIGURE 1).

Of course, it will be understood that different amplitudes of moldstructure oscillation can be selected depending upon the application ofthe invention.

FIGURE 10 illustrates the manner in which one of the cam lobes 50-54 canbe selected to produce an optimum production rate at differing speedsand other production variables affecting the operation of the continuouscasting machine. For example, the cam lobe 50' desirably is employed, asdenoted by the shaded area 152, when the casting machine is operated atmaximum casting speeds to produce a product of relatively small crosssection. At this time the drive mechanism 10 is operated to producemaximum or near-maximum number of oscillations per minute.

When a product of medium cross section area or configuration is beingcast, the drive mechanism 10 is operated at medium speed in accordance:with the reduced casting speed. At this time, employment of the cam lobe52 provides a correspondingly more rapid return stroke of the moldstructure 70 in comparison to the necessarily slowed forward stroke toproduce a correspondingly increased production of the medium sizedcasting as denoted by the shaded curve section 154 (FIG- URES 8 and 10).If the cam lobe 50 be employed instead, the return strokes of the moldstructure 70 would become undesirably slowed with reduction in castingspeed.

In much the same manner cam lobe 54 is employed for relatively largecasting speeds in conformance with shaded graph section 156. As seenfrom FIGURE 8 the return strokes of the mold structures 70 arestill morerapid in comparison to its slower forward strokes to compensate for thestill slower operation of the drive mechanism 10 and the speed of thecasting machine.

From the foregoing it will be apparent that novel and efiicient forms ofoscillation drive mechanism have been described herein. While I haveshown and described certain presently preferred embodiments of theinvention and have illustrated presently preferred methods of practicingthe same it is to be distinctly understood that the invention is notlimited thereto but may be variously embodied and practiced within thescope of the following claims.

I claim:

1.- An oscillation drive mechanism including output camming mean, a camfollower engageable with said camming means, means for rotatablymounting said camming means, means for rotating said camming means, saidcamming means having a plurality of camming surfaces positioned thereon,means for selectively juxtaposing said camming surfaces to said camfollower, said camming means being mounted upon an elongated outputshaft for rotation therewith, slidably engageable keying meanspositioned on said shaft and on said camming means, said camming meansslidably engaging said shaft and said keying means for movementtherealong, pivoted positioning means mounted for movement generallyparallel to said output shaft, said positioning means having anextension engaging a journal therefor on said camming means for slidablymoving said camming means upon pivotal movements of said positioningmeans, means for indexing said positioning means at positions thereofcorresponding to the juxtaposition of said camming surfaces to said camfollower respectively, said indexing means including an apertured platemounted on a casing for said mechanism and a spring loaded plungermounted on said positioning means and shaped for partial insertion intosaid plate apertures.

2. An oscillation drive mechanism including output camming means, a camfollower engageable with said camming means, means for rotatablymounting said camming means, means for rotating said camming means, saidcamming means having a plurality of camming surfaces positioned thereon,means for selectively juxtaposing said camming surfaces to said camfollower, each of said camming surfaces having a constant velocitycamming portion and an accelerational camming portion, said velocityportions being of similar character and said accelerational portionsbeing of respectively differing character so that movements of said camfollower in one direction thereof by said velocity portions are atsubstantially the same constant velocity for a given speed of saidmechanism irrespective of the preselected one of said camming surfacesbut movements of said cam follower in the opposite direction thereofunder control of said accelerational portions occur at correspondinglydiffering accelerational rates at said given speed.

3. The combination according to claim 2 wherein each of said cammingsurfaces includes a pair of constant velocity portions and a pair ofaccelerational portions arranged in an alternating array.

4. The combination according to claim 2 wherein each of saidaccelerational portions induces similar acceleration and decelerationalmovements of said cam follower in said opposite direction at each ofsaid correspondingly differing rates.

5. The combination according to claim 2 wherein each of said velocityportions includes similar accelerational and decelerational sectionsadjacent the beginning and ending thereof respectively.

6. In a continuous casting machine, the combination comprising a moldstructure mounted for oscillatory movement, an oscillational lever, anoscillational drivin-g mechanism having a support, a cam followerpivotally mounted on said support, means for pivotally mounting saidoscillational lever and for connecting said lever to said cam followerand to said mold structure, said driving mechanism including cammingmeans and means for rotata-bly mounting and driving said camming means,said camming means having a plurality of camming surfaces formedthereon, said camming means being slidably and keyingly mounted upon ashaft forming part of said driving means for rotation with said shaft,and means for slidably moving said camming means along said shaft forengaging a selected one of said camming surfaces with said cam followerto impart a correspondingly oscillatory character to the movements ofsaid mold structure.

7. The combination according to claim 6 wherein said joining means forsaid lever and said cam follower include a pivoted link and a pluralityof pivot connections for said link formed on said cam follower forimparting correspondingly differing amplitudes of movement of said leverand said mold structure for each of said camming surfaces.

8. The combination according to claim 6 wherein each of said cammingsurfaces includes a constant velocity portion for moving said moldstructure at a constant rate in a forward direction at a given speed ofsaid driving means, and said camming surfaces further include arespectively dilfering accelerational camming portion so that saidcamming surfaces return said mold structure at correspondingly differingspeeds.

References Cited UNITED STATES PATENTS 678,409 7/1901 Lengweiler 74-541,720,189 7/1929 Jackson 74-568 2,295,041 9/1942 Iunghans 164833,258,815 7/1966 Reinfeld 16426O FRED C. MATTERN, JR., Primary Examiner.

W. S. RATLIFF, JR., Assistant Examiner.

U.S. Cl. X.R. 745 68

